As the related techniques of the optical power monitoring device using APD, Patent Documents 1 and 2 shown below will be described.
Patent Document 1 discloses an APD bias voltage control circuit. This APD bias voltage control circuit is constituted with: a light receiving unit which receives an optical signal by an APD and converts it to an electric signal; and an APD bias voltage control unit which gives an optimum bias voltage to the APD. The APD bias voltage control unit is constituted with: a direct current voltage source which is capable of controlling an output voltage; a variable resistor connected between the direct current voltage source and the APD; and a CPU which performs various kinds of controls. The variable resistor is connected in series to the APD and gives a bias voltage to the APD.
Patent Document 2 discloses a light receiver which uses an APD as a light receiving element. This light receiver calculates the magnification corresponding to the intensity of an inputted optical signal of the APD and divides a value acquired by simply converting an APD current to a voltage with that value to linearize the relation between the intensity of the inputted optical signal and the voltage of the inputted optical signal.
Patent Document 1: Japanese Unexamined Patent Publication 2002-084235 (ABSTRACT, FIG. 4, and the like)
Patent Document 2: Japanese Unexamined Patent Publication 2004-289206 (ABSTRACT, FIG. 1, and the like)
As described above, the optical power monitoring device using the APD is broadly used in the fields of optical communications and the like. Further, it is desired to achieve higher speed and higher precision with the optical power monitoring device.
It is therefore an object of the present invention to provide an optical power monitoring device and the like capable of further achieving the speed and precision further, which is the issue described above.